Total Recorder Professional - Condense AVI File

I'm a senior and challenged! I have Total Recorder Professional. I work from home and attend training webinars which I tape--2 hours long. At first I just did audio...then did audio/video. Merrily saving them as AVI file until my C drive told me it's full.

Within the TR Program it gives me some options to Save File as...should I choose MPEG4?

Can I bring the prior AVI files back in to TR and save them as MPEG4?

I don't mind researching if someone will give me a "clue" what direction I should be going in.

Also, I looked on the Forum for a box to "Search" for Total Recorder and all I found was the Google box that takes you out on the internet? How do I search within the Forum?